Lung
Size, Shape and Location
Manatees have unique lungs. Unlike other mammals, manatee lungs are flattened-out
and long. They are positioned lengthwise along the back.

Can
you find the lungs?(Click
on diagram to enlarge)

The
real deal: Long lungs

Amount
of Air Exchange/CapacityThe
manatee's amount of air exchange/capacity is massive.How
do humans compare? How do scientists measure lung volume? Manatees Hugh
and Buffet at Mote Marine Laboratory have actually been trained to exhale
into a device called a "spirometer". Watch the video below--who
do you think has the most lung power?

The manatee's
amount of air exchange is higher than any other mammal's. Humans are thought
to exchange only about 10% in a breath.

In contrast,
the rate of exchange of air in the manatee's lungs is very quick
and very complete. In a single breath, manatees can exchange about 90%
of the air that is in their lungs. This is even more amazing because
manatees only breathe through their nostrils. They don't breathe
through their mouth.

To achieve
such a large air exchange, manatees will blow out or exhale very
forcefully when they reach the water surface, and then breathe in
or inhale. Manatees have muscles in the bronchials and a very muscular
diaphragm, which helps to facilitate rapid air exchange.

Because of
this large air exchange, manatees take in more oxygen with each breath.
That allows them to stay underwater longer between breaths. While resting,
a manatees can stay underwater for as long as 20 minutes before
coming up for another breath.

The lengthy
manatee lungs also help them to rise and fall in the water, and spread
out the bouyancy very effectively along the length of the body helping
them to float
.

"That
Thing Got A Hemi?"
Another unique anatomical feature of manatees is that instead of having
a diaphragm that divides the animal in half across the chest ,
they have a hemi-diaphragm, like two diaphragms, that runs the
length of much of their torso. And each of these lungs can exchange air
separately. This is a huge benefit, and just works in their favor for
any animal that has been hit by a boat and had one of the lungs injured.
Though one lung is no longer functional, the animal is still able to survive
using the other lung. There are some animals in the wild that scientists
have seen with this injury, and you can see the manatee sort of lists
to one side, they're a little crooked in the water. But such a manatee
is still using the uninjured lung and they're able to get by with just
that one lung exchanging.

Try
This!Investigations/Journaling

1. How Much Air Do You Exchange In One Breath?
After a normal breath, exhale. Then without inhaling again, blow out.
It's quite amazing how much more air can be expelled from one's lungs
with the extra effort! This short demonstration helps you realize how
little air humans exchange during normal breathing. When you blew out
after exhaling, there was still a lot more air in your lungs to exchange.

2.
Comparing Your Lungs How are your lungs situated in your body? What shape are they?
How does the size of your lungs compare to the size of a manatees? Compare
these and other aspects of your lungs to manatee lungs, and summarize
the similarities and differences in your journal.

3. What makes it possible for animals as large as manatees
to easily float and move in water? Write your ideas, then try these investigations
into density and the properties of salt water. summarize your new understandings
in your journal.

4.
Underwater mammals differ in many ways from mammals that live
on land. In what ways are land mammals and underwater mammals similar?
What common characteristics qualify both groups of animals to be called
mammals?